Interferometric modulation of radiation

ABSTRACT

An Interferometric Modulator (IMod) is a microelectromechanical device for modulating light using interference. The colors of these devices may be determined in a spatial fashion, and their inherent color shift may be compensated for using several optical compensation mechanisms. Brightness, addressing, and driving of IMods may be accomplished in a variety of ways with appropriate packaging, and peripheral electronics which can be attached and/or fabricated using one of many techniques. The devices may be used in both embedded and directly perceived applications, the latter providing multiple viewing modes as well as a multitude of product concepts ranging in size from microscopic to architectural in scope.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation and claims priority from theU.S. application Ser. No. 10/844,802, filed May 12, 2004, now U.S. Pat.No. 7,280,265, which is a divisional of U.S. application Ser. No.10/078,282, filed Feb. 19, 2002 now U.S. Pat. No. 7,042,643, which is adivisional of U.S. application Ser. No. 09/991,378, filed Nov. 21, 2001,which is a continuation of U.S. application Ser. No. 08/769,947, filedDec. 19, 1996, now abandoned, which is a continuation-in-part of U.S.application Ser. No. 08/238,750, filed May 5, 1994, now U.S. Pat. No.5,558,950, and a continuation-in-part of U.S. application Ser. No.08/544,630, filed Nov. 6, 1995, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to visible spectrum (which we define to includeportions of the ultra-violet and infrared spectra) modulator arrays andinterferometric modulation.

The first patent application cited above describes two kinds ofstructures whose impedance, the reciprocal of admittance, can beactively modified so that they can modulate light. One scheme is adeformable cavity whose optical properties can be altered bydeformation, electrostatically or otherwise, of one or both of thecavity walls. The composition and thickness of these walls, whichcomprise layers of dielectric, semiconductor, or metallic films, allowsfor a variety of modulator designs exhibiting different opticalresponses to applied voltages.

The second patent application cited above describes designs which relyon an induced absorber. These designs operate in reflective mode and canbe fabricated simply and on a variety of substrates.

The devices disclosed in both of these patent applications are part of abroad class of devices which we will refer to as IMods (short for“interferometric modulators”). An IMod is a microfabricated device thatmodulates incident light by the manipulation of admittance via themodification of its interferometric characteristics.

Any object or image supporter which uses modulated light to conveyinformation through vision is a form of visual media. The informationbeing conveyed lies on a continuum. At one end of the continuum, theinformation is codified as in text or drawings, and at the other end ofthe continuum, it is abstract and in the form of symbolic patterns as inart or representations of reality (a picture).

Information conveyed by visual media may encompass knowledge, stimulatethought, or inspire feelings. But regardless of its function, it hashistorically been portrayed in a static form. That is, the informationcontent represented is unchanging over time. Static techniques encompassan extremely wide range, but in general include some kind of mechanismfor producing variations in color and/or brightness comprising theimage, and a way to physically support the mechanism. Examples of theformer include dyes, inks, paints, pigments, chalk, and photographicemulsion, while examples of the latter include paper, canvas, plastic,wood, and metal.

In recent history, static display techniques are being displaced byactive schemes. A prime example is the cathode ray tube (CRT), but flatpanel displays (FPD) Offer promise of becoming dominant because of theneed to display information in ever smaller and more portable formats.

An advanced form of the FPD is the active matrix liquid crystal display(AMLCD). AMLCDs tend to be expensive and large, and are heavy users ofpower. They also have a limited ability to convey visual informationwith the range of color, brightness, and contrast that the human eye iscapable of perceiving, using reflected light, which is how real objectsusually present themselves to a viewer. (Few naturally occurring thingsemit their own light.)

Butterflies, on the other hand, achieve a broad range of color,brightness, and contrast, using incident light, processedinterferometrically, before delivery to the viewer.

SUMMARY

In general, in one aspect, the invention features a modulator of lighthaving an interference cavity for causing interference modulation of thelight, the cavity having a mirror, the mirror having a corrugatedsurface.

In general, in another aspect of the invention, the interferencemodulation of the light produces a quiescent color visible to anobserver, the quiescent color being determined by the spatialconfiguration of the modulator.

In implementations of the invention, the interference cavity may includea mirror and a supporting structure holding the mirror, and the spatialconfiguration may include a configuration of the supporting structure,or patterning of the mirror. The supporting structure may be coupled toa rear surface of the mirror. The invention eliminates the need forseparately defined spacers and improves the fill-factor.

In general, in another aspect of the invention, the structure formodulating light includes modulators of light each including aninterference cavity for causing interference modulation of the light,each of the modulators having a viewing cone. The viewing cones of themodulators are aligned in different directions.

In implementations of the invention, the viewing cones of the differentmodulators may be aligned in random directions and may be narrower thanthe viewing cone of the overall structure. Viewing a randomly orientedarray of interference modulators effectively reduces the color shift.

In general, in another aspect of the invention, the modulators may besuspended in a solid or liquid medium.

In general, in another aspect of the invention, an optical compensationmechanism is coupled to the modulators to enhance the opticalperformance of the structure. In implementations of the invention, themechanism may be a combination of one or more of a holographicallypatterned material, a photonic crystal array, a multilayer array ofdielectric mirrors, or an array of microlenses. The brightness and/orcolor may be controlled by error diffusion. An array of modulators maybe viewed through a film of material which, because of its tailoredoptical properties, enhances the view from a limited range of angles, ortakes incident light of random orientation and orders it. The film mayalso enhance the fill factor of the pixel. The film may also comprise apatterned light emitting material to provide supplemental lighting.

In general, in another aspect of the invention, an optical fiber iscoupled to the interference cavity. The invention may be used in theanalysis of chemical, organic, or biological components.

In general, in another aspect of the invention, there is an array ofinterference modulators of light, a lens system, a media transportmechanism and control electronics.

In general, in another aspect, the invention features an informationprojection system having an array of interference modulators of light, alens system, mechanical scanners, and control electronics. Inimplementations of the invention, the control electronics may beconfigured to generate projected images for virtual environments; andthe array may include liquid crystals or micromechanical modulators.

In general, in another aspect, the invention features an electronicsproduct having an operational element, a housing enclosing theoperational element and including a display having a surface viewed by auser, and an array of interference modulators of light on the surface.

Implementations of the invention may include one or more of thefollowing features. The operational element may include a personalcommunications device, or a personal information tool, or a vehicularcontrol panel, or an instrument control panel, or a time keeping device.The array may substantially alter the aesthetic or decorative featuresof the surface. The aesthetic component may respond to a state of use ofthe consumer product. The array may also provide information. Themodulation array of the housing may comprise liquid crystals, fieldemission, plasma, or organic emitter based technologies and associatedelectronics.

In general, in another aspect, the invention features devices in whichaggregate arrays of interference modulators are assembled as a display,e.g., as a sign or a billboard.

In general, in another aspect, the invention features a vehicle having abody panel, an array of interference modulators of light on a surface ofthe body panel, and electronic circuitry for determining the aestheticappearance of the body panel by controlling the array of interferencemodulators.

In general, in another aspect, the invention features a buildingcomprising external surface elements, an array of interferencemodulators of light on a surface of the body panel, and electroniccircuitry for determining the aesthetic appearance of the surfaceelements by controlling the array of interference modulators.

In general, in another aspect, the invention features a full coloractive display comprising a liquid crystal medium, and interferometricelements embedded in the medium.

In general, in another aspect, the invention features a structureincluding a substrate, micromechanical elements formed on the substrate,and electronics connected to control the elements, the electronics beingformed also on the substrate.

Individual pixels of the array may consist of arrays of subpixels,allowing brightness and color control via the activation of somefraction of these subpixels in a process known as spatial dithering.Individual pixels or subpixel arrays may be turned on for a fraction ofan arbitrary time interval to control brightness in a process known aspulse width modulation (PWM). Individual pixels or subpixel arrays maybe turned on for a fraction of the time required to scan the entirearray to control brightness in a process known as frame width modulation(FWM). These two schemes are facilitated by the inherent hysteresis ofthe IMod which allows for the use of digital driver circuits.Neighboring pixels yield a brightness value which is the average of thedesired value when error diffusion is used. Brightness control may beachieved via a combination of spatial dithering, PWM/FWM, or errordiffusion. Color control may be achieved by tuning individual colors toa particular color, or by combining pixels of different colors anddifferent brightness. The terms pixels and IMods are interchangeable,but in general, pixel refers to a controllable element which may consistof one or more IMods or subpixels, and which is “seen” directly orindirectly by an individual.

The arrays may fabricated on a solid substrate of some kind which may beof any material as long as it provides a surface, portions of which areoptically smooth. The material may be transparent or opaque. Thematerial may be flat or have a contoured surface, or be the surface of athree dimensional object. The arrays may be fabricated on the surface,or on the opposite or both sides if the substrate is transparent. In afurther aspect the invention can be viewed in a variety of ways.

Implementations of the invention may include one or more of thefollowing features. The array may be directly viewed in that anindividual can look at the array and see the represented informationfrom any angle. The array may be directly viewed from a fixed angle. Thearray may be indirectly viewed in that the information is projected onto a secondary surface, or projected through an optical system, or both.

In yet another aspect the invention can be electrically controlled anddriven in several ways.

Implementations of the invention may include one or more of thefollowing features. The array may be fabricated on a substrate and thedriver and controller electronics are fabricated on a separatesubstrate. The two substrates may be connected electrically or opticallyvia cables, or optically, magnetically, or via radio frequencies via afree space connection. The array may be fabricated with driver,controller, or memory electronics, or some combination thereof, mountedon the same substrate and connected via conducting lines. The array maybe fabricated on a substrate along with the driver, controller or memoryelectronics, or some combination thereof. The substrate may includeactive electronics which constitute driver, controller, or memoryelectronics, or some combination thereof, and the array may befabricated on the substrate. The electronics may be implemented usingmicroelectromechanical (MEM) devices.

In an additional aspect the invention modulates light actively, using anarray of modulators or sections of arrays which are addressed in severalways.

Implementations of the invention may include one or more of thefollowing features. Individual pixels or arrays of pixels may beconnected to a single driver and may be activated independently of anyother pixel or pixel array in a technique known as direct addressing.Individual pixels or arrays of pixels may be addressed using atwo-dimensional matrix of conductors and addressed in a sequentialfashion in a technique known as matrix addressing. Some combination ofmatrix or direct addressing may be used.

Among the advantages of the invention are one or more of the following.

Because interference modulators are fabricated on a single substrate,instead of a sandwich as in LCDs, many more possible roles are madeavailable. The materials used in their construction are insensitive todegradation by UV exposure, and can withstand much greater variations intemperature. Extremely saturated colors may be produced. Extremely highresolutions make possible detail imperceptible to the human eye. Eithertransmitted or reflected light may be used as an illumination source,the latter more accurately representing how objects and images areperceived. The ability to fabricate these devices on virtually anysubstrate makes possible the surface modulation of essentially anyman-made or naturally occurring object. It is possible to realize imageswhich are much closer to what exists in nature and more realistic thanwhat is possible using current printing methods.

Interferometric modulation uses incident light to give excellentperformance in terms of color saturation, dynamic range (brightness),contrast, and efficient use of incident light, performance which mayapproach the perceptual range of the human visual system. Thefabrication technology allows interference modulators to be manufacturedin a great variety of forms. This variety will enable active visualmedia (and superior static visual media) to become as ubiquitous as thetraditional static media which surround us.

In general, the invention provides the tools for creating an array ofproducts and environments which are as visually rich and stimulating asanything found in nature.

Other advantages and features will become apparent from the followingdescription and from the claims.

DESCRIPTION

FIGS. 1A and 1B are top and perspective views of an IMod with spatiallydefined color.

FIG. 2 is a side view of an IMod with spatially defined color.

FIGS. 3A and 3B are top and side views of a spatially defined mirror.FIG. 3A shows a mirror with a 50% etch while FIG. 5B shows a mirror witha 75% etch.

FIG. 4 is a perspective view of a back-supported IMod with a good fillfactor.

FIGS. 5A, 5B, and 5C are schematic views of an IMod and IMod array witha limited viewing cone. FIG. 5A shows the behavior of light within theviewing cone while FIG. 5B shows the behavior of light outside the cone.FIG. 5C shows the performance of an overall array.

FIGS. 6A, 6B, 6C, 6D, and 6E, 6F are side views of optical compensationmechanisms used for minimizing color shift and enhancing fill factor.FIG. 6A shows a holographically patterned material, FIG. 6B shows aphotonic crystal array, FIG. 6C shows a multilayer dielectric array,FIG. 6D shows an array of microlenses, while FIGS. 6E and 6F show sideand top views of a supplemental lighting film.

FIGS. 7A and 7B are schematic views of an array which is addressed usingspatial dithering. FIG. 7A shows a full-color pixel while FIG. 7B showsdetail of a sub-pixel.

FIG. 8 is a timing diagram for driving a binary. IMod.

FIG. 9 is a diagram of the hysteresis curve for an IMod device.

FIGS. 10A and 10B are a top view of an IMod array which is connected formatrix addressing and a digital driver. FIG. 10A shows the matrix arraywhile FIG. 10B shows a digital driving circuit.

FIG. 11 is a side view of an IMod array configured for direct viewing.

FIG. 12 is a side view of an IMod array configured for direct viewingthrough an optical system.

FIG. 13 is a diagram of an IMod array configured for indirect viewing.

FIG. 14 is a perspective view of an IMod array and a separatedriver/controller.

FIGS. 15 and 16 are perspective views of IMod arrays anddriver/controllers on the same substrates.

FIGS. 17A and 17B are front views of a direct driven IMod subarraydisplay. FIG. 17A shows a seven segment display while FIG. 17B showsdetail of one of the segments.

FIGS. 18A and 18B are top views of a matrix driven subarray display.FIG. 18A shows a matrix display while FIG. 18B shows detail of one ofthe elements.

FIG. 19 is a side view of an IMod based fiber optic endcap modulator.

FIG. 20 is a perspective view of a linear tunable IMod array.

FIGS. 21A and 21B are a representational side view of a linear IModarray used in an imaging application and a components diagram. FIG. 21Ashows the view while FIG. 21B shows the components diagram.

FIG. 22 is a perspective view of a two-dimensional tunable IMod array.

FIG. 23 is a perspective view of a two-dimensional IMod array used in animaging application.

FIGS. 24A, 24B, 24C, 24D, and 24E are views of an IMod display used in awatch application. FIG. 24A shows a perspective view of a watch display,FIGS. 24B, 24C, 24D, and 24E show examples of watch faces.

FIGS. 25A and 25B are views of an IMod display used in a head mounteddisplay application. FIG. 25A shows a head mounted display while FIG.25B shows detail of the image projector.

FIGS. 26A, 26B, 26C, and 26D are perspective views of an IMod displayused in several portable information interface applications and acomponents diagram. FIG. 26A shows a portable information tool, FIG. 26Bshows the components diagram, FIG. 26C shows a cellular phone, whileFIG. 26D shows a pager.

FIGS. 27A, 27B, 27C, 27D, 27E, 27F and 27G are views of an IMod displayused in applications for information and decorative display, a remotecontrol, and components diagrams. FIGS. 27A, 27B, and 27D show severalexamples, FIG. 27C shows a components diagram, FIG. 27E shows a remotecontrol, and FIG. 27F shows another components diagram.

FIGS. 28A and 28B are side views of an IMod display used in anapplication for automotive decoration and a components diagram. FIG. 28Ashows a decorated automobile while FIG. 28B shows the componentsdiagram.

FIGS. 29A, 29B, and 29C are views of an IMod array used as a billboarddisplay and a components diagram. FIG. 29A shows a full billboard, FIG.29B shows a display segment, FIG. 29C shows a segment pixel, and FIG.29D shows the components diagram.

FIGS. 30A and 30B are views of an IMod array used as an architecturalexterior and a components diagram. FIG. 30A shows the skyscraper, whileFIG. 30B shows the components diagram.

FIGS. 31A and 31B are drawings of a liquid crystal impregnated with aninterferometric pigment. FIG. 31A shows the liquid crystal cell in theundriven state while FIG. 31B shows it in the driven state.

FIGS. 32A and 32B are drawings of an IMod array used in a projectiondisplay and a components diagram. FIG. 32A shows the projection systemwhile FIG. 32B shows the components diagram.

FIGS. 33A and 33B are drawings of an IMod array used in an chemicaldetection device and a components diagram. FIG. 33A shows the detectiondevice while FIG. 33B shows the components diagram.

FIGS. 34A, 34B, and 34C are front and side views of an IMod basedautomotive heads up display and a components diagram. FIG. 34A shows thefront view, FIG. 34B shows the side view, and FIG. 34C shows thecomponents diagram.

FIGS. 35A and 35B are drawings of an IMod display used in an instrumentpanel and a components diagram. FIG. 35A shows the panel while FIG. 35Bshows the components diagram.

IMod Structures

Referring to FIGS. 1A and 1B, two IMod structures 114 and 116 eachinclude a secondary mirror 102 with a corrugated pattern 104 etched intoits upper (outer) surface 103, using any of a variety of knowntechniques. The corrugation does not extend through the membrane 106 onwhich the mirror is formed so that the inner surface 108 of the mirrorremains smooth. FIG. 1B reveals the pattern of etched corrugation 104 onthe secondary mirror and the smooth inner surface 112 which remainsafter etch. The corrugated pattern, which can be formed in a variety ofgeometries (e.g., rectangular, pyramidal, conical), provides structuralstiffening of the mirror, making it more immune to variations inmaterial stresses, reducing total mass, and preventing deformation whenthe mirror is actuated.

In general, an IMod which has either no voltage applied or somerelatively steady state voltage, or bias voltage, applied is consideredto be in a quiescent state and will reflect a particular color, aquiescent color. In the previously referenced patent applications, thequiescent color is determined by the thickness of the sacrificial spacerupon which the secondary mirror is fabricated.

Each IMod 114, 116 is rectangular and connected at its four corners tofour costs 118 via support arms such as 120 and 122. In some cases (seediscussion below), the IMod array will be operated at a stated constantbias voltage. In those cases, the secondary mirror 102 will alwaysmaintain a quiescent position which is closer to corresponding primarymirror 128 than without any bias voltage applied. The fabrication ofIMods with differently sized support arms allows for the mechanicalrestoration force of each IMod to be determined by its geometry. Thus,with the same bias voltage applied to multiple IMods, each IMod maymaintain a different biased position (distance from the primary mirror)via control of the dimensions of the support arm and its resultingspring constant. The thicker the support arm is, the greater its springconstant. Thus different colors (e.g., red, green, and blue) can bedisplayed by different IMods without requiring deposition of differentthickness spacers. Instead, a single spacer, deposited and subsequentlyremoved during fabrication, may be used while color is determined bymodifying the support arm dimensions during the single photolithographicstep used to define the arms. For example, in FIG. 2, IMods 114, 116 areboth shown in quiescent states with the same bias voltage applied.However, the cap spacing 126 for IMod 114 is larger than gap spacing 128for IMod 116 by virtue of the larger dimensions of its respectivesupport arms.

As shown in FIGS. 3A and 3B, in another technique for achievingspatially defined color, instead of affecting the quiescent position ofthe movable membrane, one or both of the mirrors (walls) comprising theIMod is patterned to determine its qualities spatially instead of bymaterial thickness.

Thus, in FIG. 3A, mirror 300 has two layers 302 and 304. By etchinglayer 302 the effective index of refraction of layer 302, and thus theperformance of mirror 300, may be altered by controlling the percentageof the layer which remains after the etch. For example, a material withindex of 2 maintains that value if there is no etch at all. However if75% of the material is etched away, the average index falls to 1.75.Etching enough of the material results in an index which is essentiallythat of air, or of the material which may fill in the etched area.

The mirror layer 308 in FIG. 3B, by contrast has an effective refractiveindex which is less than that of mirror layer 302. Because the overallbehavior of both mirrors is determined by their materials properties,and the behavior of the IMod by the mirror properties, then the color ofan IMod incorporating mirror 300 is different from an IMod comprisingmirror 306 by virtue of spatially varying, e.g., etching or patterning,one or more of the layers comprising the mirrors. This, again, can bedone in a single photolithographic step.

Referring to FIG. 4, in another type of IMod a back supporting mechanismis used instead of an array of posts and support arms (which consumeuseful surface area on the display). Here, the secondary mirror 402 ismechanically held by support arm 400 at location 406. Arm 400 contactsthe substrate 403 at locations 408 where it occupies a minimalfootprint, thereby maximizing the amount of area devoted to the mirrors402, 404. This effect is enhanced by notches 408, 410 which allowmirrors 402 and 404 to conform to the support. Rear support could alsobe achieved in other ways, perhaps using multiple arms to maintainparallelism. The rear supports can also provide a basis for multilevelconductor lines. For example, an elevated conductor line 412 may be tiedto support arm 400. This configuration minimizes the area on thesubstrate required for such purposes.

Reducing Color Shift and Supplying Supplemental Illumination

As shown in FIGS. 5A through 5C, to minimize color shift as the angle ofincidence changes (a characteristic of interferometric structures) IModstructures 502, 506 are fabricated to have a very high aspect ratio,i.e., they are much taller than they are wide. Consequently, they onlyexhibit interferometric behavior within a narrow cone 501 of incidenceangles. Incident light 500 which is within cone 501, as in FIG. 5A,interacts with the multiple layers (shown by striped sections in thefigure) the composition and configuration of which are dictated by thedesign of the IMod. In general, as indicated in the previous patentapplications, these can consist of combinations of thin films of metals,metallic oxides, or other compounds. The important fact being that thegeometry of the stack dictates that interference occurs only within anarrow cone of incidence angles on the other hand, as seen in FIG. 5B,incident light 504 (outside of the cone) is relatively unaffected by theIMod because it interacts with only a very few layers. Such an IModwould appear, say blue, to a viewer who looks at it from a narrow rangeof angles.

As seen in FIG. 5C, if an array 507 of these structures 508 isfabricated such that they are oriented to cover many different viewingangles then the entire array can appear blue from a much larger range ofangles. This random orientation may be achieved, for example, byfabrication on a randomly oriented surface or by random suspension in aliquid medium.

As seen in FIGS. 6A-6F, other techniques for minimizing color shift andfor supplying supplemental illumination are possible. In these examples,a specially designed optical film is fabricated on the opposite surfaceof the substrate from the surface on which the IMod array resides. Suchfilms can be designed and fabricated in a number of ways, and may beused in conjunction with each other.

In FIG. 6A, film 600 is a volume or surface relief holographic film. Avolume holographic film may be produced by exposing a photosensitivepolymer to the interference pattern produced by the intersection of twoor more coherent light sources (i.e. lasers). Using the appropriatefrequencies and beam orientations arbitrary periodic patterns ofrefractive indices within the film may be produced. A surface reliefholographic film may be produced by creating a metal master using anynumber of microfabrication techniques known by those skilled in the art.The master is subsequently used to the pattern into the film. Such filmscan be used to enhance the transmission and reflection of light within adefinable cone of angles, thus minimizing off-axis light. The colors andbrightness of a display viewed with on axis light are enhanced and colorshift is diminished because brightness goes down significantly outsideof the cone.

In FIG. 6B, another approach is shown as device 604 in which an array ofstructures 606 is fabricated on the substrate. These structures, whichcan be fabricated using the techniques described in the previouslyreferenced patent applications, can be considered photonic crystals, asdescribed in the book “Photonic Crystals”, by John D. Joannopoulos, etal., and incorporated by reference. They are essentiallythree-dimensional interferometric arrays which demonstrate interferencefrom all angles. This provides the ability to design waveguides whichcan perform a number of functions including channeling incident light ofcertain frequencies to the appropriately colored pixels, or by changinglight of a certain incidence angle to a new incidence angle, or somecombination of both.

In another example, seen in FIG. 6C, a three-layer polymeric film 610contains suspended particles 611. The particles are actually single ormulti-layer dielectric mirrors which have been fabricated in the form ofmicroscopic plates. These plates, for example, may be fabricated bydeposition of multilayer dielectric films onto a polymer sheet which,when dissolved, leaves a film which can “ground up” in a way whichproduces the plates. The plates are subsequently mixed into a liquidplastic precursor. By the application of electric fields during thecuring process, the orientation of these plates may be fixed duringmanufacture. The mirrors can be designed so that they only reflect at arange of grazing angles. Consequently, light is either reflected ortransmitted depending on the incidence angle with respect to the mirror.In this case, layer 612 is oriented to reflect light 609 of highincidence that enters the film 610 closer to the perpendicular. Layer614 reflects light 613 of lower incidence into a more perpendicularpath. Layer 616 modifies the even lower angle incident light 615.Because the layers minimally affect light which approachesperpendicularly, they each act as a separate “angle selective incidencefilter” with the result that randomly oriented incident light couplesinto the substrate with a higher degree of perpendicularly. Thisminimizes the color shift of a display viewed through this film.

In another example, FIG. 6D, micro lenses 622 are used in an array indevice 620. Each lens 622 may be used to enhance the fill factor of thedisplay by effectively magnifying the active area of each pixel. Thisapproach could be used by itself or in conjunction with the previouscolor shift compensation films.

In another example, FIG. 6E, device 624 uses supplemental lighting inthe form of a frontlighting array. In this case an organic lightemitting material 626, for example, Alq/diamine structures andpoly(phenylene vinylene), can be deposited and patterned on thesubstrate. The top view, FIG. 6F, reveals a pattern 627 whichcorresponds with the IMod array underneath. That is, the light emittingareas 626 are designed to obscure the inactive areas between the IMods,and allow a clear aperture in the remaining regions. Light is emittedinto the substrate onto the IMod and is subsequently reflected back tothe viewer. Conversely, a patterned emitting film may be applied to thebackplate of the display and light transmitted forward through the gapsbetween the sub-pixels. By patterning a mirror on the front of thedisplay, this light can be reflected back upon the IMod array.Peripherally mounted light sources in conjunction with films relying ontotal internal reflection are yet another approach.

Brightness Control

Referring to FIG. 7A, a full color spatially dithered pixel 701 includesside-by-side sub-pixels 700, 702, and 704. Sub-pixel 700, for example,includes sub-arrays of IMods whose numbers differ in a binary fashion.For example, sub-array 706 is one IMod, sub-array 708 is 2 IMods,sub-array 710 is 4 IMods, while sub-array 718 is 128 IMods. Sub-array712 is shown in greater detail in FIG. 7B. In the arrays, each IMod isthe same size so that the amount of area covered by each sub-array isproportional to the total number of IMods in the array. Row electrodes724 and column electrodes 722 are patterned to allow for the selectiveand independent actuation of individual sub-arrays. Consequently, theoverall brightness of the pixel may be controlled by actuatingcombinations of the sub-arrays using a binary weighting scheme with atotal of a sub-arrays, each sub-pixel is capable of 256 brightnesslevels. A brightness value of 136 may be achieved, for example, by theactuation of sub-arrays 718 and 712. Color is obtained by combiningdifferent values of brightness of the three sub-pixels.

The apparent dynamic range of the display may also be enhanced using aprocess known as error diffusion. In some applications, the number ofbits available for representing the full range of brightness values(dynamic range) may be limited by the capabilities of the drivers, forexample. In such a situation, the dynamic range may be enhanced bycausing neighboring pixels to have a brightness value, the average ofwhich is closer to an absolute value that cannot be obtained given theset number of bits. This process is accomplished electronically withinthe controller logic, and can be accomplished without significantlyaffecting the display resolution.

Digital Driving

In a digital driving scheme, as shown in FIGS. 8, 9, and 10, FIG. 8 is atiming diagram showing one set of voltages required to actuate a matrixaddressed array of IMods. Column select pulses 800 and 802 arerepresentative of what would be applied to a particular column. Furtherdetail is revealed in pulse 800 which is shown to switch from voltagelevel Cbias to voltage Cselect. Row select pulses 804 and 806 are alsoshown, with 804 revealing that the required voltage levels are Rselect,Rbias, and Roff (O volts). When a column select pulse is present, and arow select pulse is applied, the pixel which resides at the intersectionof the two is actuated as shown in the case of pixel 808 which resideson the row driven by select pulse 804, and subsequently in pixel 810,which resides on the row driven by pulse 806. When select pulse 804 isdriven to the Roff level, pixel 808 is turned off. Pixel 812 illustratesthe behavior of a pixel in an arbitrary state when a R of f value isplaced on the row line, i.e., if it is on it turns off, or if it is offit remains off.

In FIG. 9, the voltages are shown in the context of a hysteresis curvewhich is typical of an IMod. As the applied voltage is increased, themembrane does not move significantly until the value rises beyond acertain point, which is known as the collapse threshold. After thispoint, the membrane undergoes full displacement. This state ismaintained until the voltage is dropped below a point where actuationbegan. Several conditions must be met in order for this scheme to besuccessful. The combination of Csel and Rsel must be higher than thecollapse threshold voltage, the combination of Cbias and Rsel must notfully actuate the membrane, the combination of Cbias and Rbias mustmaintain a displaced state, and the combination of Roff and Cbias mustfree the membrane.

FIG. 10A is representative of a typical matrix addressed arrayillustrating column lines 1000 and row lines 1002. FIG. 10B illustratesa typical shift register based driver circuit. The size of the displayarray and the number of bits in the resister would determine how many ofthese components would be required for both rows and columns. Bitscorresponding to the appropriate row and column values are shifted intothe register and loaded on the outputs when they are required during thecourse of the scanning the display.

Viewing Modes

Referring to FIG. 11, among the different generic ways to view an IModdisplay 1104 (the best one being selected based on the particularproduct application) are a direct viewing mode with the viewer 1100perceiving the display without the aid of an image forming opticalsystem. Direct viewing can occur in reflection mode, using reflectedlight 1102, or transmitted mode, using transmitted light 1106, or somecombination of the two.

In another example, FIG. 12, direct viewing configurations may rely onintervening optics to form an image from an image source generated byIMod display 1204. Reflected light 1202 or transmitted light 1212, or acombination of the two, may be manipulated by macro lens system 1206. Amore complicated or space critical application might require moreelaborate optics. In such a case, a lens system might be implementedusing a micro-lens array 1208 with or without the aid of redirectionmirrors 1214.

In FIG. 13, indirect viewing may be achieved with respect to an imagegenerated by display 1304 using either transmitted light 1310 orreflected light 1301 from light source 1300. Lens system 1302 is thenused to form an image on viewing surface, 1306, which is where theviewer perceives the image.

Packaging and Driving Electronics

Referring to FIGS. 14 through 16, different techniques for packaging andproviding driver electronics are illustrated in order of degree ofintegration. FIG. 14 shows a configuration requiring two separatesubstrates. The IMod display array resides on substrate 1400 which couldbe any one of a variety of materials described in the referenced patentapplications. The IMod array is not shown because it is obscured bybackplate 1404, which is bonded to substrate 1400 via seal 1402.Backplate 1404 can also be of a number of different materials with theprimary requirement being that it be impermeable to water, and that itsthermal coefficient of expansion be close to that of the substrate. Seal1402 can be achieved in a number of ways. One approach involves theapplication of an epoxy but this results in the generation of gasesduring the curing process which may interfere with the operation of thedevices. Another approach involves fusion or eutectic bonding whichutilizes heat to create a chemical or diffusion bond between twomaterials, in this case the substrate and the backplate. This processmay be enhanced by forming a bead, in the form of seal 1402, ofadditional materials such as silicon, aluminum, or other alloys whichtend to bond well. This process may be further enhanced using atechnique known as anodic bonding. This is similar to fusion bondingexcept that a voltage potential is applied across the backplate andsubstrate. This allows the bond to occur at a lower temperature. Othertechniques are also possible.

The electronics 1410 comprise all of the row and column drivers, memory,and controller logic required to actuate the IMods in a controlledfashion. Exactly where each of these functions reside would depend onthe application and degree of integration required for an application.Specific examples will be discussed in subsequent portions of thispatent application. In FIG. 14, the drive electronics 1410 are shownmounted on substrate 1412. A connection is made between this substrate1412 and the display substrate 1400, by ribbon cable 1408 andsubsequently to the display array via conductors 1406. Many techniquesexist for patterning the fine array of conductors for ribbon cable, aswell as for connecting them to disparate substrates.

FIG. 15 shows a display where the electronics have been mounted on thedisplay substrate. Display substrate 1500 serves as a support not onlyfor the IMod array but also for the integrated circuits 1508. Conductors1506 are patterned to create appropriate paths between the ICs and thearray. ICs 1508 may be mounted on the substrate using a number oftechniques including TAB mounting and chip-on-glass techniques whichrely on anisotropically conducting films.

FIG. 16 shows a display which includes fully integrated electronics andcan be achieved in two fundamental ways.

In one case, substrate 1600 is an electronically inactive medium uponwhich the IMod array and electronics 1608 are fabricated separately orin a fabrication process with some overlap. Electronics may befabricated using a number of techniques for building thin filmtransistors using materials such as amorphous silicon, polysilicon, orcadmium selenide. Electronics may also be fabricated usingmicroelectromechanical (MEM) switches instead of, or in conjunction withthin film transistors. All of these materials are deposited on thesurface of the substrate, and provide the electronically orelectromechanically active medium for circuits. This implementationdemonstrates a powerful approach to surface micromachining, which couldbe described as epi-fab. Essentially, in epi-fab all components of anymicroelectromechanical structure, both the mechanical and theelectronic, are fabricated entirely on the surface of an inertsubstrate.

In the second case, the substrate is active silicon or gallium arsenideand the electronics are fabricated as a part of it. The IMod array isthen fabricated on its surface. The electronics may also include morecomplex electronic circuits associated with the particular applications.Application specific circuits, e.g., microprocessors and memory for alaptop computer can be fabricated as well, further increasing the degreeof integration.

FIGS. 17A and 17B show two drive/connection schemes. Direct drive isillustrated by a seven segment display 1700. A common conductor 1702connects all of the segments 1703 in parallel. In addition, separatesegment conductors 1704 go to each segment individually. As shown inFIG. 17B, in a detailed corner 1712 of one segment, an array of IMods1708 are connected in parallel and would be connected as a group to asegment conductor 1704 and the common conductor 1702. The generalmicroscopic nature of this type of IMod structure makes it necessary togroup the IMods together to form larger elements to allow for directviewing of the display. Application of a voltage between a selected oneof the segment conductors and the common conductor actuates all of theIMods within that segment. The direct drive approach is limited by thefact that the number of conductors becomes prohibitive if the number ofgraphical elements gets large enough.

Referring to FIGS. 18A and 18B, an active matrix drive approach isshown. Row lines 1800 and column lines 1804 result in a two-dimensionalarray the intersections of which provide pixel locations such as 1802.As seen in FIG. 18B, each of the pixel locations 1802 may be filled withan array of parallel connected IMods 1803. In this scheme a commonconductor 1808 may be connected to the row line, and the IMod arrayconductor, 1810, may be connected to the column line, though this couldbe reversed.

Product and Device Applications

The remaining figures illustrate product and device applications whichuse the fabrication, drive, and assembly techniques described thus far.

The IMod as an easily fabricated, inexpensive, and capable modulator canbe placed in an exceptional number of roles which require themanipulation of light. These areas fall into at least two categories:IMods which are used to modulate or otherwise affect light for purposeswhich do not result in direct visually perceived information (embeddedapplications); and IMods which are used to convey codified, abstract orother forms of information via light to be visually perceived by anindividual (perceived applications). All of these applications, bothembedded and perceived, can be roughly divided according to array sizeand geometry, however these boundaries are for descriptive purposes onlyand functional overlap can exist across these categories. They do notrepresent an exhaustive list of possibilities.

One category of applications utilizes single or individual modulatorswhich are generally for embedded applications. These may be coupled tooptical fibers or active electronics to provide, among other things, amechanism for selecting specific frequencies on a wavelength divisionmultiplexed fiber-optic communication system, as well as a low data ratepassive fiber optic modulator. Single modulators may be coupled tosemiconductor lasers to provide, among other things, a mechanism forselecting specific frequencies transmitted by the laser, as well as alow data rate laser modulator. Single modulators may be coupled tooptical fibers, lasers, or active electronics to alter the phase oflight reflected.

Linear arrays, though generally for embedded applications, also begin tohave potential in perceived roles. Devices for printing imagery mayutilize a linear array as the mechanism for impressing information on toreflected or transmitted light which is subsequently recorded in a lightsensitive medium. Devices for scanning images may utilize a linear arrayto select different colors of a printed or real image for subsequentdetection by a light sensitive device.

Yet another category of applications includes microscopictwo-dimensional arrays of IMods which may be used to providereconfigurable optical interconnects or switches between components.Such arrays may also be used to provide optical beam steering ofincident light. Using a lens system, to be discussed later, may allowsuch an array to be readable.

Small arrays, on the order of 2″ square or smaller, may find a varietyof uses for which this size is appropriate. Applications include directview and projection displays. Projection displays can be usedindividually or in arrays to create virtual environments (VEs). Atheater is an example of a single channel VE, while an omnimax theater,with many screens, represents a multi-channel virtual environment.Direct view displays can be used for alphanumeric and graphic displaysfor all kinds of consumer/commercial electronic products such ascalculators, cellular phones, watches and sunglasses (active or static),jewelry, decorative/informative product labels or small format printing(business card logos, greeting card inserts, product labels logos,etc.); decorative clothing patches or inserts (sneakers, badges, beltbuckles, etc.); decorative detailing or active/static graphic printingon products (tennis rackets, roller blades, bike helmets, etc.); anddecorative detailing or active/static graphic printing on ceramic,glass, or metal items (plates, sculpture, forks and knives, etc.). Verylarge (billboard sized) displays may be produced by combining arrays ofsmall arrays which are themselves directly driven. Embedded applicationsmay include spatial light modulators for optical computing and opticalstorage. Modulator arrays fabricated on two dimensional light sensitivearrays, such as CCDs, may be used as frequency selective filter arraysfor the selection of color separations during image acquisition.

Another size category of devices, medium arrays, may be defined byarrays of roughly 2″ to 6″ square. These include direct view displaysfor consumer electronic products including organizers, personal digitalassistants, and other medium sized display-centric devices; controlpanels for electronic products, pocket TVs, clock faces (active andstatic); products such as credit cards, greeting cards, wine and otherproduct labels; small product exteriors (walkmen, CD cases, otherconsumer electronic products, etc.); and larger active/static graphicalpatches or inserts (furniture, clothing, skis, etc.)

For arrays on the order of 6″ to 12″ square, large arrays, there existother compelling applications. These include direct view displays forlarge format display-centric products (TVs, electronic readers fordigital books, magazines and other traditionally printed media, specialfunction tools); signs (window signs, highway signs, public informationand advertising signs, etc.); large consumer product exteriors/activesurfaces and body panels (microwave oven, telephone, bicycle, etc.); andfurniture exteriors and lighting fixtures, high end products. Directview 3-D displays and adaptive optics are also possible.

Arrays approximately 12″ square or larger, and aggregate arrays (whichare combinations of smaller arrays to achieve a larger one), furtherdefine a unique set of devices, and provide the potential to affect ouroverall environment. These include direct view displays for very largeformats (billboards, public spaces, highway, industrial/militarysituation displays, etc.); Body panels and active exteriors for verylarge products (cars, motorcycles, air and water craft, sails,refrigerators); and active/static exteriors/interiors for very largeobjects (buildings, walls, windows).

In FIG. 19, a fiber optic detector/modulator 1901 includes a single IMod1904. An optical fiber 1900 is bonded to substrate 1902. IMod 1904resides on the substrate which is bonded to backplate 1910 by a seal1908 using anodic bonding for example. The backplate also serves as asubstrate for detector 1906. Electronics 1912 are mounted on substrate1902 via chip-on-glass or some other previously described technique.Device 1901 could provide a number of functions depending on the natureof the IMod. For example, a reflective mode IMod could act as amodulator of light which is incident through the optical fiber. Using adesign which switches between absorbing or reflecting, the intensity ofthe reflected light may be modulated. Using a transmissive IMod, thedevice could act as a transceiver. Switching the IMod between fullytransmissive or fully reflective would also modulate the reflected lightand thus perform as a data transmitter. Holding it in the fullytransmissive state would allow the detector 1906 to respond to lightincident through the fiber, thus acting like a receiver. Use of atunable IMod would allow the device to act as a frequency sensitivedetector, while not precluding modulation as well.

Referring to FIGS. 20 and 21A, a linear array 2104 of IMods 2001, 2003,2005 is supported on a substrate 2004. Each of the IMods includes aprimary mirror 2006, a secondary mirror 2002, electrodes 2008, supportarms 2000, and support plate 2010. Each IMod would be driven separatelyin a binary or analog fashion depending on the application. In therepresentative application shown in FIG. 21A, a transport mechanism 2106moves a medium 2108 past a linear IMod array 2104 (the axis of the arrayis into the page). Two potential applications for such a configurationcould include image acquisition or digital printing. In acquisitionmode, component 2100 is a detector array which is coupled to IMod array2104 via lens system 2102. Component 2110 acts as a light source,illuminating pre-printed images which reside on media 2108. By using theIMod as a tunable filter array, specific colors of the image on themedia may be selected and detected, allowing for high resolution captureof graphical information residing on the media.

Alternatively, component 2100 could be a light source which uses lenssystem 2102 to couple and collimate light through IMod array 2104 ontomedia 2108. In this case, the media would be a photosensitive materialwhich would undergo exposure as it passed beneath the array. This wouldprovide a mechanism for the printing of high resolution color images. Noelectronic components reside on the array substrate in this example.FIG. 21B shows a components diagram illustrating one way in which thisproduct could be implemented using off-the-shelf components. In thiscase, they comprise a central controller 2112, (including processor2114, memory 2116, and low level I/O 2118), high level I/O components(user interface 2120 and logic 2122, detector array 2130), controlcomponents (light source 2132, media transport 2128 and logic 2126),display 2140 (logic 2138, drivers 2136, IMod array 2134) and powersupply 2124. The central controller handles general purpose operationalfunctions, the high level I/O components and display dictate howinformation gets in and out of the product, and the controllercomponents manipulate peripheral devices.

Referring to FIG. 22, a two-dimensional IMod device 2201 is fabricateddirectly on a photosensitive detector array 2206 such as a chargecoupled device (CCD) or other light sensitive array. Array 2206 hasphotosensitive areas 2202 and charge transport and IMod driveelectronics 2204. Planarization layer 2208, deposited on the CCD,provides a flat surface for the fabrication of the IMod array 2200. Sucha layer could be in the form of a curable polymer or spun-on oxide.Alternatively, some form of chemical mechanical polishing might be usedto prepare an optically smooth surface on the integrated circuit. Device2201 provides a fully integrated 2-D, tunable light detection systemwhich can be used for image capture or image printing (if the detectoris replaced with a light source).

FIG. 23 illustrates a digital camera 2301 based on this device. Camerabody 2300 provides mechanical support and housing for lens system 2304and electronics and IMod detector array 2302. Scene 2306 is imaged onthe surface of the array using the lens system. By tuning the IMod arrayto the frequencies of light corresponding to red, green, and blue, afull color image may be acquired by combining successive digitalexposures. Hyperspectral imagery (in other wavelength regions such asultraviolet or infrared) may be obtained by tuning to frequenciesbetween these points. Because of the high switching speed of the IMods,all three images may be acquired in the time it takes a conventionalcamera to capture one.

Referring to FIG. 24A, an application for small-sized displays is adigital watch 2400 (the back side of the watch is shown in FIG. 24A)which includes a reflective IMod display at its core. The IMod displaycomprises an IMod array 2402 and drive electronics, 2404. The display(see examples in FIGS. 24B-24E) could vary in complexity from separategraphic elements driven in a direct drive manner, to a dense array usingactive matrix addressing, or some combination. The electronics could befabricated on glass using polysilicon or amorphous silicon transistors,or MEM switches. While the direct drive approach would still exploit thesaturated appearance of the IMod, a dense array would allow for theselection of arbitrary or pre-programmed graphical patterns such as FIG.24B. This would add an exciting new fashion component to watches notunlike the art oriented Swatch® only in electronic form. Owners couldselect from a series of preprogrammed displays 2408 (FIG. 24D), say bypushing the stem, or download limited edition displays digitally fromtheir favorite artists.

Referring to FIG. 25A, a small transmissive IMod array is shown in ahead mounted display 2511. Support 2508 provides a frame for mountingthe display components and the viewer screen 2512. Referring also toFIG. 25B, the display includes a light source 2500, an IMod array 2502,a lens system 2504, and a reflector 2506. The display is used inindirect mode with the image formed on screens 2512 for the benefit ofviewer 2510. Alternatively, the IMod array could be formed directly onthe screen itself and thus be used in direct view mode. In both cases,the display could function to provide aesthetic imagery which could beseen by other individuals and provide an appealing dynamic externallook.

Referring to FIGS. 26A through 26D, an IMod display 2604 is shown in aproduct with a very wide range of applications. In this case, thedisplay is used in direct view mode, and could come in a variety ofsizes depending on the specific product, but ranging in size fromseveral inches across to about one foot diagonal. The primary goal isfor a device that has a very small footprint and/or is portable, and thescheme is to facilitate mobility. The device 2600 could be described asa personal information tool, a portable digital assistant, a webbrowser, or by various other titles which are only now being coined todescribe this class of products. In general its purpose would be toserve as a media interface for a variety of information gathering,processing, and dissemination functions, or as a mobile or stationaryperipheral for a centralized processing station to which it isconnected, perhaps via the internet or some wireless communicationsmedium. A specialized peripheral in a home-based application might be akitchen cooking assistant which would be portable and present easilyreadable recipes by virtue of the display and the fact that most of itsprocessing is located in some other unit. Many other variations on thistheme are possible. This tool comprises a display 2604 and some basiccontrols 2602. Internal components would include some combination ofprocessing electronics, information storage, and communicationshardware. Representative products range from personal organizers anddigital books and magazines, to application specific tools(construction, medical, scientific) or tools for browsing the internet.Techniques for operating such a tool are varied and could range fromvoice recognition, to touch sensitive screens. However, all of theproducts would have the ability to digitally display graphicalinformation using reflected (preferred) or transmitted light with highlysaturated colors. Because it is digital, the complexity and cost of thedriving electronics would be significantly reduced, and because it canuse reflected light, the power consumption is extremely low while theperformance remains high. These two characteristics make such a highperformance display oriented product viable from an economic andportability perspective. FIG. 26C is an example of one kind of personalcommunications device, a cellular phone in this case though the pager ofFIG. 26D is an example of another. Display 2608 is capable of displayingboth graphical and text information. FIG. 26B shows a components diagramillustrating one way in which these products could be implemented usingavailable off-the-shelf components. In this case, they comprise acentral controller 2610 (including processor 2612, memory 2614, and lowlevel I/O 2616), high level I/O components (user interface 2618 andlogic 2620, audio I/O 2624, digital camera 2628, and wireless tranceiver2630), display 2638 (logic 2636, drivers 2634, IMod array 2632) andpower supply 2622. The central controller handles general purposeoperational functions, while high level I/O components dictate howinformation gets in and out of the product.

Referring to FIG. 27A through 27G, several applications are shown whichemphasize the aesthetic nature of an IMod display as well as itsinformation conveying aspect. An IMod display could be included in aportable compact disc player 2700 of the kind that serves as a commoditystatus device made by many manufacturers. By virtue of an IMod display,a larger fraction of the exterior of the player may be devoted toinformation display functions, indicating status of the device as wellas tracks playing. Because it consumes such a large fraction of theexterior, it would be possible to have the display play a moresignificant role in the appearance of the CD player. Static as well asdynamic patterns and images could be displayed which may or may not haveany connection with the status of the player. However, because of therich saturated colors, the appearance becomes a significant and distinctselling point for the manufacturer. This concept holds true for anynumber of consumer electronic devices whose form and function could beenhanced by an active exterior. A microwave oven which pulsed red whenthe food was done, or a bread baking machine whose exterior changedcolors as the baking process progressed are just two examples. FIG. 27Cshows a components diagram illustrating one way the CD player could beimplemented using off-the-shelf components. In general, they comprise acentral controller 2706 (including processor 2707, memory 2710, and lowlevel I/O 2712), high level I/O components (user interface 2702 andlogic 2704), display 2722 (logic 2720, drivers 2718, IMod array 2716)disc player mechanism 2714, and power supply 2724. The centralcontroller handles general purpose operational functions, high level I/Ocomponents dictate how information gets in and out of the product, andthe disc play mechanism manipulates mechanical servos.

The skis of FIG. 27D and the sneaker of FIG. 27F are examples ofconsumer goods which could benefit purely from the aesthetic potentialfor an active exterior. In both cases, an IMod array has been fabricatedon a substrate, for example flexible plastic, along with electronics andintegrated into the product using any number of techniques currentlyused for incorporating or laminating composite pieces into fabric orsolid composites. Power could be supplied by piezoelectric like deviceswhich convert the mechanical power of movement (e.g., ski flexing orwalking) into electricity. Remote control, FIG. 27E, could be used toeffect control over the images displayed. Further control could beexhibited to reflect the mode of use of the product. In the case of theskis, the pattern might become more dynamic as the skier gained speed,or in the case of the shoes the strength of the runner's stride. Theseare only a few of the possibilities for the aesthetic enhancement ofconsumer goods by the use of a dynamic exteriors. FIG. 27G illustrateshow a display could respond to the state of the consumer product. Thecontrol mechanism would consist of a sensor 2730, which could detectvibration (in a shoe or ski) or temperature (in a turkey), program logic2732, which would interpret the sensor output and provide preprogrammed(or reprogrammable) images or image data to display 2734, communicationsinput/output 2738, and display control electronics 2736.

Referring to FIGS. 28A and 28B, even larger IMod arrays are shownincorporated into the exterior of an automobile. In this case bodypanels 2800, 2802 as well as windows 2804, could use reflective andtransmissive IMod designs respectively. Dynamic control of the exteriorappearance of a car would be a very appealing option for the owner,providing the ability for the owner to customize the appearance himself,or to “download” exteriors in a digital fashion. Such a control 2806could take the form of a small panel integrated into the dashboard whichdisplayed various exteriors under button control. The same techniquescould be applied to other highly style oriented goods in the class andfunctional category, including motorcycles, sailboats; airplanes andmore. FIG. 28B shows a components diagram illustrating one way in whichthis product could be implemented using off-the-shelf components. Ingeneral, they comprise a central controller 2808 (including processor2810, memory 2812, and low level I/O 2814), high level I/O components(user interface 2816, and logic 2818), display 2828 (logic 2826, drivers2824, IMod array 2822) and power supply 2820. The central controllerhandles general purpose operational functions, while high level I/Ocomponents dictate how information gets in and out of the product.

Referring to FIGS. 29A through 29D, billboard-sized arrays 2900 of IModdisplay segments could be assembled and replace current static displaysused for advertising and public service announcements. Display 2900would include reflective devices to be illuminated by ambient light or asupplemental light source 2902. A large display could be assembled fromindividual segments 2904 (FIG. 29B) which would support segment pixels2906. Each segment pixel would include three sets of sub-pixel arrays2910, 2912, and 2914, which would reside on pixel substrate 2908 (FIG.29C). The resulting large displays could range from placards on thesides of buses and inside of subways, to billboards, to entirearchitectural structures such as homes or skyscrapers. In FIG. 30A,skyscraper 3000 is an example of a large building which exploits theaesthetic and cheap manufacture of the IMod array. All of the glass usedin the manufacture of such structures is coated with thin films up to 4or more layers thick to provide energy efficient coatings. Similarcoating techniques could be applied to the manufacture of the IModarrays. FIG. 30B shows a components diagram illustrating one way inwhich both of these products could be implemented using off-the-shelfcomponents. In this case, they comprise a central controller 3002(including processor 3004, memory 3006, and low level I/O 3006), highlevel I/O components (PC based user interface 3008), display 3020 (logic3018, drivers 3016, IMod array 3014), lighting control 3012, and powersupply 3010. The central controller handles general purpose operationalfunctions, high level I/O components dictate how information gets in andout of the product, and the controller components manipulatesupplementary lighting and peripheral components.

It should be noted that several alternative display technologies mayalso be applicable to some of the less rigorous aesthetic applications,in particular, small AMLCDs, LCDs fabricated on active crystallinesilicon, field emission displays (FEDs), and possibly plasma baseddisplays these technologies are deficient due to their price,manufacturing complexity, and non-reflective (emissive) operation.However, certain high-end fashion oriented products (luxury watches,jewelry and clothing) may command a price and provide an environmentwhich could make these viable approaches. Organic emitters could beparticularly suited for exterior applications which are not necessarily,exposed to environmental extremes and which might be seen in dimly litsituations. They are the only emissive technology which offers thepotential for very low-cost and ease of manufacture. The Alq/diaminestructures and poly(phenylene vinylene) materials, which were describedbefore, could be patterned and directly addressed on a variety ofsubstrates (plastic clothing inserts for example) to provide dynamicexteriors.

FIG. 31A shows interferometric particles suspended in a liquid crystalmedium, 3100, making possible full color liquid crystal displays basedon the controlled orientation of the particles within the medium. Asshown in FIG. 31B, application of a voltage between electrodes 3102 fromsource 3104 causes the particles to be driven from their randomquiescent orientation 3106 defined by the liquid crystal and thesurfaces of the substrate into an orderly orientation 3108. When theparticles are randomly oriented, light of a specific color 3110 isreflected. When the particles are ordered, light 3112 passes through.

Referring to FIG. 32A, two kinds of projection display units, 3200 and3202, are shown. Each unit comprises components consisting of lightsource/optics 3206, electronics 3204, projection optics 3210, and IModarray 3208. While the IMod array in projector 3200 is designed for usein transmission mode, the IMod array in projector 3202 is designed foruse in reflection mode. The other components are essentially the samewith the exception of the need to modify the optics to accommodate thedifference in the nature of the optical path. Screen 3212 shows arepresentative projected image. FIG. 32B shows a components diagramillustrating one way in which this product could be implemented usingoff-the-shelf components. In this case, they comprise a centralcontroller 3212 (including processor 3214, memory 3216, and low levelI/O 3218), high level I/O components (user interface 3220 and logic3222), display 3236 (logic 3234, drivers 3232, IMod array 3230)focus/light source control 3226, and power supply 3224. The centralcontroller handles general purpose operational functions, high level I/Ocomponents dictate how information gets in and out of the product, andthe controller components manipulate peripheral devices.

An application in chemical analysis is illustrated in FIG. 33A.Transparent cavity 3300 is fabricated such that gas or liquid medium3302 may pass through its length. Light source 3304 is positioned toproject broad spectrum light through the medium into tunable IMod array3306. This array could be coupled to a fiber 3308, or reside on adetector array with 3308 acting as data link to electronics 3310. Byspectrally analyzing the light which passes through the medium, much canbe determined about its composition in a compact space. Such a devicecould be used to measure the pollutants in an air stream, the componentsin a liquid, separations in an chromatographic medium, fluorescingcompounds in a medium, or other analytes which can be measured usinglight, depending on the frequency of the light source. FIG. 33B shows acomponents diagram illustrating one way in which this product could beimplemented using off-the-shelf components. In this case, they comprisea central controller 3312 (including processor 3314, memory 3316, andlow level I/O 3318), high level I/O components (user interface 3320, andlogic 3322), IMod drivers 3330 and IMod 332B, light source 3326, andpower supply 3324. The central controller handles general purposeoperational functions, high level I/O components dictate how informationgets in and out of the product, and the controller components manipulateperipheral devices.

FIG. 34A illustrates an automotive application from a driver'sviewpoint. FIG. 34B represents a side view of the windshield anddashboard. A direct view graphical display 3404 portrays a variety ofinformation, for example, an enhanced view of the roadway. An imagegenerated in the windshield via a heads-up display. Such a display is avariation on the previously discussed projection system. In this case,the inside of the windshield acts as a translucent projection screen,and the projector 3406 is mounted in the dashboard. Automotiveapplications have very stringent requirements for heat, and UVstability, as well as high brightness ambient conditions which would beideal for an IMod application. FIG. 34C shows a components diagramillustrating one way in which these products could be implemented usingoff-the-shelf components. In this case, they comprise a centralcontroller 3410 (including processor 3412, memory 3414, and low levelI/O 3416), high level I/O components (user interface 3418, digitalcamera 3428, auto sensors 3424), display 3436 (logic 3434, drivers 3432,IMod array 3430) and power supply 3422. The central controller handlesgeneral purpose operational functions, high level I/O components dictatehow information gets in and out of the product, and the controllercomponents manipulate peripheral devices.

FIG. 35A portrays an application involving an instrument panel, in thiscase an oscilloscope 3500, though many kinds of special purpose toolscould benefit from a graphical display. In this situation, display 3502,is used to show a waveform plot but could also, as described previously,display text, or combinations of graphics and text. Portable low-powertools for field use would benefit greatly from a full-color fastresponse FPD. FIG. 35B shows a components diagram illustrating one wayin which these products could be implemented. All of the components areavailable off-the-shelf and could be configured by one who is skilled inthe art. In this case, they comprise a central controller 3530(including processor 3510, memory 3514, and low level I/O 3516), highlevel I/O components (user interface 3518 and logic 3520), display 3534(logic 3532, drivers 3530, IMod array 3528) and power supply 3522. Thecentral controller handles general purpose operational functions, whilehigh level I/O components dictate how information gets in and out of theproduct.

Other embodiments are within the scope of the following claims.

1. A personal communication device comprising: a housing; an operationalelement enclosed within the housing; communications hardware coupled tothe operational element; and a display element connected to theoperational element, wherein the display element comprises an array ofinterference modulators of light.
 2. The device of claim 1, wherein eachof the interference modulators comprises a first mirror layer and asecond mirror layer, and wherein the first mirror layer has a refractiveindex which is less than that of the second mirror layer.
 3. The deviceof claim 1, wherein the personal communication device comprises acellular radiotelephone.
 4. The device of claim 1, wherein the personalcommunication device comprises a pager.
 5. A personal information toolcomprising: a housing; an operational element enclosed within thehousing; input controls coupled to the operational element; and adisplay element connected to the operational element, wherein thedisplay element comprises an array of interference modulators of light.6. The personal information tool of claim 5, wherein each of theinterference modulators comprises a first mirror layer and a secondmirror layer, and wherein the first mirror layer has a refractive indexwhich is less than that of the second mirror layer.
 7. The personalinformation tool of claim 5, wherein the personal information toolcomprises a portable digital assistant (PDA).
 8. The personalinformation tool of claim 5, wherein the personal information toolcomprises a laptop computer.
 9. A control panel comprising: a housing;an operational element enclosed within the housing; a sensor coupled tothe operational element configured to provide information to theoperational element; and a display element connected to the operationalelement, and configured to display the information provided by thesensor, wherein the display element comprises an array of interferencemodulators of light.
 10. The control panel of claim 9, wherein each ofthe interference modulators comprises a first mirror layer and a secondmirror layer, and wherein the first mirror layer has a refractive indexwhich is less than that of the second mirror layer.
 11. The device ofclaim 9, wherein the control panel comprises a vehicular control panel.12. The control panel of claim 9, wherein the control panel comprises aninstrument control panel.
 13. A fashion product comprising: a housingcoupled to a fabric; an operational element enclosed within the housing;and a display element connected to the operational element, wherein thedisplay element comprises an array of interference modulators of light.14. The fashion product of claim 13, wherein each of the interferencemodulators comprises a first mirror layer and a second mirror layer, andwherein the first mirror layer has a refractive index which is less thanthat of the second mirror layer.
 15. The fashion product of claim 13,wherein the fashion product comprises a shoe.
 16. The fashion product ofclaim 13, wherein the fashion product comprises an article of clothing.17. A kitchen appliance comprising: a housing; an operational elementenclosed within the housing; a sensor configured to provide informationto the operational element, wherein the information is indicative of acooking process; and a display element connected to the operationalelement, and configured to provide a display based on the informationprovided by the sensor, wherein the display element comprises an arrayof interference modulators of light.
 18. The kitchen appliance of claim17, wherein each of the interference modulators comprises a first mirrorlayer and a second mirror layer, and wherein the first mirror layer hasa refractive index which is less than that of the second mirror layer.19. The kitchen appliance of claim 17, wherein the kitchen appliancecomprises a microwave oven.
 20. The kitchen appliance of claim 17,wherein the kitchen appliance comprises a bread baking machine.
 21. Avehicle having a device, the device comprising: a housing; anoperational element enclosed within the housing; and a display elementconnected to the operational element and positioned on an exteriorsurface of the vehicle, wherein the display element comprises an arrayof interference modulators of light.
 22. The device of claim 21, whereineach of the interference modulators comprises a first mirror layer and asecond mirror layer, and wherein the first mirror layer has a refractiveindex which is less than that of the second mirror layer.
 23. The deviceof claim 21, wherein the device is configured to display an aestheticfeature on the display element in response to a state of use of thevehicle.
 24. The device of claim 21, wherein the device is configured todisplay an aesthetic feature which is downloaded or derived from anexternal source.
 25. The device of claim 21, wherein the device isconfigured to display an aesthetic feature on the display element, andwherein the aesthetic feature comprises graphics.
 26. A devicecomprising: an operational element having a display element, wherein thedisplay element comprises an array of interference modulators of lighton a viewable surface, and wherein liquid crystals, field emission,plasma, or organic emitter based technologies and associated electronicsare used as the array of interference modulators.
 27. A devicecomprising: an operational element having a display element, wherein thedisplay element comprises aggregate arrays of interference modulators oflight, and wherein the arrays are used to display information on signsor billboards.
 28. The device of claim 27, wherein each of theinterference modulators comprises a first mirror layer and a secondmirror layer, and wherein the first mirror layer has a refractive indexwhich is less than that of the second mirror layer.
 29. A projectiondisplay unit comprising: a housing; an operational element enclosedwithin the housing; a modulation element connected to the operationalelement, wherein the modulation element comprises an array ofinterference modulators of light; and a light source, wherein light fromthe light source is transmitted through the array of interferencemodulators so as to project an image.